Containers made of tin or multicolored sheet metal, glass or else ceramic, common in the past, are increasingly being replaced by containers made of plastic. Recently, wide-necked plastic containers have been used for the packaging of fluid substances, for example bulk material for applications in the home, in agriculture, industry and trade, etc. The low weight and the lower costs play a significant role in this substitution. To this end, the use of recyclable plastic materials and the overall total energy balance in their production contribute to promoting the acceptance of wide-necked plastic containers by users.
Single-layer or multi-layer wide-necked plastic containers are often produced using so-called extrusion-blow-molding, such as a hose blowing method. The extrusion-blow-molding machines used for extrusion-blow-molding can have one or more extruders for feeding the required plastic material. The output of the extruder is connected to an extruder head, into whose exhaust nozzle—which can be regulated in the opening width—the extruded hose exits. The extruded plastic hose can be made in one or more layers. The hose that exits continuously or almost continuously from the exhaust nozzle is delivered to a blow-mold-tool arrangement and inflated by overpressure using a blow pin that is run into the molding cavity. Then, the inflated wide-necked plastic container is demolded from the molding cavity.
Bulk material, such as sugar, flour, coffee, powder for instant beverages, powdered milk, baby food, etc., is in many cases stored in wide-necked plastic containers, which have a large opening in relation to a periphery at the transition from the container shoulder to the container body, so that the removal of the bulk material, for example with a metering spoon, is facilitated. The container neck that has the opening can have a rotationally symmetrical—for example circular, square, rectangular, or oval—cross-section. It is understood that based on the manufacturing process, the “corners” of a square or rectangular neck section are designed actually rounded, i.e., have a radius. In general, a heat-sealing film is applied on the edge of the opening, for example glued or bonded, in order to close the container interior. The opening is ultimately covered by a closure cap, which can be pressed on the open end of the wide-necked plastic container. In this case, locking means that project from an inside wall of the closure cap engage behind corresponding stopping means, which are molded-on below the opening onto the outside wall of the container neck. In the case of a known wide-necked plastic container, the locking means that project from the inside wall of the closure cap are combined to form a single, annular circumferential rib. In an analogous way, the stopping means on the outside wall of the container neck are also designed as an annular circumferential stopping projection. The actual closure can be designed as, for example, a pivoting cover part or the like, which is hinged, for example, on the top of the closure cap.
In the case of wide-necked plastic containers with a circular cross-section of the container neck, in general a sufficiently good locking of the closure cap on the container neck is ensured. Also, the rotationally-symmetrical container neck facilitates the mounting of the closure cap by the relative orientation of the parts to one another in general playing no role. In the case of wide-necked plastic containers with a rectangular or oval container neck, however, the closure cap must be oriented correctly for mounting, so that the latter is not canted during pressing. In addition, the closure cap can be loosened relatively simply from the container by rotating it relative to the container. This is, of course, unacceptable in applications in which tamper resistance must be ensured. The consumer of a product that is dispensed in the wide-necked plastic container must be able to be confident that the container contents are present in the quality delivered by the dispenser and that the contents have not been tampered with. Therefore, in the case of such wide-necked plastic containers, additional locking devices are usually provided. The latter must, however, be manufactured very exactly and in precisely the correct location so that even in the most disadvantageous case of the manufacturing tolerances of the container neck and the closure cap, the play between the two parts remains small, so that a secure attachment of the closure cap to the container neck is ensured. Very stringent requirements, which directly correlate to elevated tool costs, follow for the tools for the production of the closure cap and for the blow-mold tools for the production of the wide-necked plastic container.